Technical Field
The invention relates to a thermal release element.
Background Information
Thermal release elements have been known and in use for a long time. They are used, in particular, in large numbers in sprinkler systems and fire extinguishing systems, in which they are disposed at outlet nozzles or sprinkle outlets connected to tubing filled with a pressurized extinguishing agent (generally water), while maintaining the former in the closed position, between a thrust bearing and a closure element. If the outside temperature exceeds the release temperature to be set by corresponding and known technical measures, the frangible material of the outer wall is destroyed as a result of the build-up of the pressure with increasing temperature of the release fluid, the release element shatters and allows the closure element to open, so that the extinguishing agent is able to exit the sprinkler nozzles or sprinkler outlets and be discharged.
Aside from an application in such sprinkler systems and fire extinguishing systems, applications are also known and described, in which such release elements close pressure relief openings, in order to release them at a release temperature exceeding a critical temperature, for example, in order to timely drain compressed gas containers in cases of fire before the latter are able to explode, for example. Applications of release elements of this type are also known in connection with the interruption of a flow of electrical current. Other applications are conceivable; such release elements may always be used whenever temperature-sensitive mechanical switch positions must be changed or else electrical lines must be interrupted.
The typically known thermal release elements of the aforementioned kind, known for many years and of which one, for example, is shown and described in DE 36 01 203 A1, consistently had and have a circular or else, based on a circular target shape, a cross-sectional shape slightly ovalized due to tolerance deviations, in the tubular middle section as seen in a sectional plane transverse, in particular perpendicular, to the axial extension of the release element. This cross-sectional shape applies in this case to both the outer contour of the outer wall as well as to the inner contour thereof, which adjoins an interior hollow space. This is because during manufacture, a tubular base material was and is used, which is initially closed at a first frontal end to form the cap-like closed end section, for example, by thermal shaping, in which the interior hollow space is then filled with the extinguishing agent, and in which the second cap-like closing and end section is formed connected to the second frontal end, for example, by repeated thermal reshaping. The tubular base material being considered here consistently was and is a tube having a nominally circular cross-section, the circular cross-sectional contour relating to both the outside of the wall as well as the inner contour of the outer wall facing the tubular area or tubular section. Deviations from the ideal circular shape, which resulted in a slight ovalization of this contour, were possible and occurred only because of potential manufacturing tolerances.
To fulfill an essential requirement of thermal release elements formed in this way, which derives from the typical assembly situation in the use, in particular, for keeping a mechanical switch position of participating elements open or closed, namely, the reliable withstanding of a force directed in the direction of an opposing switch position of the mechanical elements, which bears down on the thermal release element in its axial direction, it was previously proposed in DE 20 2013 102 312 U1, to design a container body in a release element of this type so that in a tubular middle section thereof as seen in a sectional plane transverse, in particular, perpendicular to the axial direction, it has an outer contour of the outer wall and/or an inner contour of the outer wall adjoining a hollow space situated in the interior of the container body, which deviates from a circular or oval contour. Release elements having an outer contour deviating from a circular or oval shape are also already known from U.S. Pat. Nos. 4,609,047, 4,739,835 and 1,733,701. Whereas improved response behavior (in particular, a rapid release time) is said to be achieved with the particular shape of the release elements according to U.S. Pat. Nos. 4,609,047 and 4,739,835, the attachment of ribs described in U.S. Pat. No. 1,733,701 used to improve breaking (to shatter in numerous small splinters instead of preventing the formation of merely a longitudinal crack) is described.
Another previously unaddressed problem of the rapidly responding thermal release elements, in particular, which are formed with a very thin-walled container body for a short reaction time, is a perceptible sensitivity to transverse forces characteristic of these elements. Such forces occur, for example, when the sides of the release elements are inadvertently struck or bumped, for example, as a result of an unintended collision with an object or the like carried through the space. An ideal objective in this case is that a thermal release element is optimally insensitive to such transverse forces without, however, losing its immediate response behavior and the short reaction time to increases in ambient temperature.